We purchased our 2004 Murano brand new and at first had no real problems, but then a few times the heater would not work. The dealor replaced the radiator cap a few times and that fixed it for a short periods, usually until winter was over, then in next winter we would do it again. It never did seem to blow real hot air like my Chevy truck, but is was always enough to keep the kids warm until this year. This year and last year it has gotten worse. Our warrenty is no longer and we have no heat except when we run at 3500 RPM or greater, and that is hard on the car and gas mileage. With two small kids and weather well below zero we have not been able to drive it all winter. Our local mechanic can't figure it out either and he has spent hours on the phone with Nissan dealors. Our mechanic has replaced the thermistat, a valve or two in the heating/cooling system, flushed and reflushed and bled and rebled the lines many times as specified. The heater core puts out good heat, but it does not get into the car unless we drive at those high RPM's. Our local Mechanic has gone through everything he and I could think of, we still get no heat. HELP anyone!!!!!???????

Is it RPM or SPEED related? I don't see how it could be related to rpm but speed does make sense because if you don't have the system set to recirculate the air then the faster you drive the more pressure the incoming air will use to push into your system. At any rate if your heater core is getting hot then your problem starts with the HVAC system. You need to dig into the HVAC Section of the service manual found on this site and start troubleshooting. A flap somewhere isn't opening/closing or your blower isn't operating correctly or you could have a physical clog in the vent system (like a rag, birdsnest, etc no matter how unlikely). You didn't say if you are receiving proper airflow at the vents. Can you feel a noticeable change when moving the fan speed between the lowest and highest? Do you have the same symptoms with the Air Conditioning, does it also not get cold enough?

If your AC works properly and you are getting the correct airflow for a given speed setting out of your vents then you most likely have an obstruction at/near the heater core preventing proper airflow across it.

Find that section of your manual and post more information if you want more help.

It is RPM related. If we shift into Drive - S and drive 45 mph our faster the car will runs 3500-4000+ RPM and then we get pretty good heat, still not as much as my truck, but enough. In normall driving even at 75 mph we don't hit RPM level that high and the heater does not work even at this speed. The A/C has always worked well and we do seem to get good air flow when the fan is on high, although the passenger side does seem to blow just a little harder than the drivers side. Our mechanic has had it all appart and can find no obstructions anywere. I don't know that he has actually removed the heater core, but he did say it gets very hot right at the core. He also noted that one of 4 hoses in the cooling system never heats up as hot as the other 3. He replaced the valve on that line, but it did not help.

Our Mechanic is convinced that it is some how a problem with the cooling system, but he can not figure out why or were.

I am sorry, I am not a very good mechanic my self, but I will pass any and all advice onto our mechanic. Thank you for you help and please let me know if you have any other ideas.

Seeing as how you are at the mercy of a mechanic you're stuck and have to go by what he says. If its RPM related that would cause me to lean towards the cooling system also but it just doesn't make sense. Any cooling system should make more than ample heat at idle (save for certain diesels) to blow hot air especially since he says the heater core gets hot.

Download the HVAC section of your Murano found here on the site and have a read. There are usually troubleshooting steps found at the ends with cause and effects. Could help you out.

You still have air in the cooling system. Have your mechanic re bleed the cooling system but this time lift the front of the vehicle on the lift as high as he can safely get it. Then with a spill free funnel attached to the radiator hold the rpms at about 3000-3500 and watch for the air to come out through the funnell. Vary the rpms up and down once in a while to let the air come up. Do this for about 45 minutes and you should have heat as good as your truck.

I know that my mechanic has bled the system several times with the front end in the air, but I will show him these emails and see if he has done it for that long and with everything running as suggested. Thank you all for your help. I will let you know if it works or not. Thanks

We get one heater hose luke warm on the heater core and the other one is very hot. When the RPM's are way up then both hoses are very hot. Flushing the heater core only proves that it is not clogged, it flows fine. It acts like there is not pressure on the system to push it through the heater core until the RPM's are high. It has a new Thermostate, radiator cap, and control valve on transmittions so far. Car does not over heat when idling so pump must be o.k.

My local mechanic has not charged me for anything yet, until we get the problem fixed and the "Qualified Nissan Mechanics" keeps putting a new radiator cap on the calls it good, My mechanic has talked with Nissan several times to no avail (not to mention they are over 100 miles away). I showed him the advise about the raising the front of the car. He did that, but did not do it for 45 minutes and varing the RPM (He did it for about 10 to 15 minutes with the car idling. He will try that next, but we just wanted to see if anyone had any other ideas we could try at the same time, so that when we bring it in again we can maybe do it all at once.

THERE IS AIR IN THE COOLING SYSTEM. My money is that this vehicle had the alternator up date and the radiator was removed to accomplish this resulting in air getting into the system. With proper bleeding by SOMEBODY who understands nissans can accomplish this within one hour.Follow MPE235's instructions and this time shut the engine off after you are convinced no more air is being seen in the funnel. leave the funnel on and top it off with coolant. Allow the vehicle to completely cool off. make take several hours to over nite. once its cool look to see if the coolant level went down in the funnel. MY guess it will.

That sounds good, If I remember correctly we did have a recall on sometype of a mount, I think it was altinator. Nissan did the recall, and it probably wasn't long after that that we started haveing some miner problems with it. We will try this again and do as you and blink32 have suggested.
Thanks, I will let you know if it works.

Well, we did what you guys suggested. We put the front of the car up and ran it for well over an hour varying the speed with a funal on the radiator. It bubbled twice during that time that was noticed. The it sat all night long and it sucked down a couple of more quarts of coolant. IT DID NOT WORK! We still only get heat at over 3000 RPM which is well over normal driving speeds. So now does anyone have a better idea, we have tried this one a few times with no results. We also don't get any were near the air movment on high that I get in my truck.
HELP!!! We are fed up with a car we can't drive or fix!

Well, It turns out the it was the heater core, it is completely falling apart inside. That is why it worked sometimes and not other and that is also how the air kept getting into the system. Nissan seems very unwilling to give us anything for what will cost close to $2000 to replace, but it seems it must have been faulty from the start. After replacing the core we expect all to work again.